This invention relates generally to a cordless telephone system and, in particular, to apparatus for providing a cordless telephone with a remote control function without interfering with the voice communication feature of the telephone system or tying up the subscriber's lines.
Many systems have been devised which utilize the bell of a conventional subscriber's telephone to initiate various activities. The following United States patents all disclose bell activated systems of this nature:
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In general, the ring activated systems must be initiated over land lines by calling the base station. This requires that the subscriber's phone be hung up (i.e. not in use) before a remote control function can be initiated. If the phone is in use, there exists no possible way by which a remote control function can be carried out. In an emergency situation this type of delay could be potentially dangerous. Because these systems are dependent on land lines to establish at least a part of the communication link, the mobility of the user is limited. Correspondingly, the applicability of the system is also limited. Finally, many of the ring activated systems require special adaptors that have to be wired directly into existing phone systems which might adversely affect equipment warranties or even violate service contracts.
Other monitoring and control devices have also been devised which, although not ring actuated, carry information over land lines or existing A.C. power lines. The following United States patents disclose systems of this nature:
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Here again, the mobility of the user is greatly restricted to the extent of the data lines and the user is not provided the flexibility of maintaining simultaneous voice communication along with a remote control capability. Accordingly, the usefulness of the device is restricted and the cost of initially installing and later maintaining the equipment is generally high because of the complexity of the equipment involved.